Decline and recovery of the Bellinger River turtle, Myuchelys georgesi

Abstract

Earth's sixth mass extinction event, driven by human activity, is evident across all ecosystems, with freshwater ecosystems having the highest rates of threatened or endangered species. The freshwater Bellinger River turtle Myuchelys georgesi is an Australian native species currently at risk of extinction. Endemic to the Bellinger Drainage on the mid-north coast of NSW, M. georgesi is geographically restricted and rapidly declined in 2015, most likely owing to an outbreak of disease - a novel nidovirus (now referred to as the Bellinger River virus; BRV). Four hundred and thirty-three adult M. georgesi are known to have died from the disease, with the remaining population estimated at ca 150 turtles, most of which are juveniles. The survival and maturation of these juvenile turtles is imperative to prevent the extinction of M. georgesi. However, the recovery of M. georgesi may be impeded by the presence of another Australian species which is invasive in the Bellinger River - the Murray River short-necked turtle Emydura macquarii. No research to date has quantified the potential current threat of E. macquarii to M. georgesi, therefore the overall aim of this thesis is to investigate the potential threat of invasive E. macquarii to the recovery of M. georgesi in the Bellinger River. The Bellinger River system presents a rare opportunity to evaluate the compounding effects of extensive disease-related mortality and an invasive species, on the potential recovery and survival of an endemic and geographically restricted freshwater turtle. Findings of the thesis have implications for management and the recovery and long-term survival of M. georgesi. With freshwater turtle populations in decline throughout Australia, it is important to manage the threats to freshwater species and implement effective conservation strategies founded in rigorous science. This thesis concludes by presenting a conundrum: what do we do about an invasive, native species? Do we let E. macquarii expansion in the Bellinger drainage run its course, or do we intervene to manage its abundance and distribution as an additional measure in the recovery of M. georgesi?

Date of Award	2021
Original language	English